1. Field of the Invention
The invention relates to a knife or flail attachment for a flail type harvester that is adapted for use at a circular rotor shaft and that enables changes of the flails and/or the flail attachment without special tools.
To permit clearance from ground obstacles the flails should be pivotally attached nearest to the periphery of the rotor shaft and should be formed as to contact the outer surface of the shaft with most of its length.
2. Description of the Prior Art
In United Kingdom Patent No. 1,144,611 -- BOMFORD & EVERSHED LIMITED, the coupling element is a U-shaped clamp comprising two parallel spaced limbs of different length, the free ends of which are adapted to enter two of the holes in the rotor shaft, and means for releasably retaining said limbs in said holes. The cross-section of the tubular shaft is of square configuration. Two opposite walls of the shaft are drilled to provide registering holes and one of the walls is provided with a hole spaced from the other holes. The longer limb is passed through the registering holes and the shorter limb extends through the spaced hole and terminates within the tubular shaft in abutment with the inner face thereof. The end of the longer limb is bent over in an opposite direction of rotation of the shaft. The clamp-like bridging piece connecting the two limbs receives a chain, at the end of which the flail is fastened.
It is hardly practicable to provide holes for such coupling elements when rotor shafts of cylindrical cross-section are used, as the boring tool has to be applied at the shaft surface at an inclined angle passing through the shaft at a radial distance from the center line. As a heavy risk it must be considered that the boring tool is drifted away from the predetermined position at the outer and the opposite inner face of the cylindrical rotor shaft wall. Moreover, the second hole for the second limb of the pre-known structure requires a further working process.
If replacement of the flail or the flail-carrying chain is necessary after damage, the longer limb must be restraightened to permit the pre-known coupling element to be drawn from the shaft. This, however, requires a special tool which is mainly unavailable in the field.
In the U.S. Pat. No. 3,765,158 -- MOTT, the coupling element comprises a pin extending diametrically through a rotor shaft of circular cross-section for pivotal receiving arms in the form of a yoke ambracing the rotor shaft. Replacement after the damage of said arms or of the flails secured to it, requires a special tool, as well.